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  1. #1

    Confused over tyre sizes

    Any help on this one is much appreciated.

    At the moment I've got Schwalbe Marathon Plus tyres which are marked 25-559 26" X 1.

    I wanted solid tyres (had too many punctures when travelling alone) so I bought some Shox G2 which are 20-559.

    I would have expected them to be the same size, 559 diameter. But the Shox fits inside the Schwalbe tyre.
    When I look at the marking on the Schwalbe it says 25" 20-559.

    I don't understand, how can one be 26" and the other be 25"?

  2. #2
    Senior Member NW-Will's Avatar
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    From what you are describing...
    I am guessing... that the markings on the Schwalbe Marathon Plus tyres are wrong, or they are hard to read etc.

    Should probably read 25-590 26" x 1"

    if you measure the wheel bead to bead diameter would be close to 590mm or with the tire fully inflated the tire diameter should be close to 25 7/8"

    that would mean you have 26" wheelchair wheels.

    If you measure bead to bead diameter on the wheel close to 559mm or with the tire fully inflated the tire diameter is 24 7/8", then you do in fact have 25" wheelchair wheels. and the solid tires may just need to stretched like crazy to get them on the rims!!

    Just guessing from what you describe.



  3. #3
    Quote Originally Posted by NW-Will View Post
    From what you are describing...
    I am guessing... that the markings on the Schwalbe Marathon Plus tyres are wrong, or they are hard to read etc.

    Should probably read 25-590 26" x 1"

    if you measure the wheel bead to bead diameter would be close to 590mm or with the tire fully inflated the tire diameter should be close to 25 7/8"

    that would mean you have 26" wheelchair wheels.

    If you measure bead to bead diameter on the wheel close to 559mm or with the tire fully inflated the tire diameter is 24 7/8", then you do in fact have 25" wheelchair wheels. and the solid tires may just need to stretched like crazy to get them on the rims!!

    Just guessing from what you describe.


    Thanks for the reply. I re-read the tyres incase I had misread and they are definitely 25-559 26" X 1.

    I then went to their website and even crazier they have both:
    25-559 (26 x 1.00)
    25-590 (26 x 1.00)
    https://www.schwalbe.com/en/wheelcha...thon-plus.html

    Weirdly they don't show a 25 X 1.00 tyre at all. So looks like their labelling is wrong, crazy.

    I've read that heating the solids to get them on is the thing to do, so maybe when I do they will fit, hopefully....

  4. #4
    Senior Member djrolling's Avatar
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    In the Wheelchair arena, 559's are referred to as 25 inch. In the cycling arena, 559's are referred to as 26 inch. I have gotten tires that were marked 24x1 3/8's and 507mm so when a tire manufacturer is confused you see why everyone else could be confused. That tire turned out to be 507mm which in the bike arena is a 24 inch but not a 24x1 3/8's that tire would be a 540mm. NW-Will gave you some spot-on information. I have never used the Shox but I have heard they are a bear to get on the rim

  5. #5
    Quote Originally Posted by djrolling View Post
    In the Wheelchair arena, 559's are referred to as 25 inch. In the cycling arena, 559's are referred to as 26 inch. I have gotten tires that were marked 24x1 3/8's and 507mm so when a tire manufacturer is confused you see why everyone else could be confused. That tire turned out to be 507mm which in the bike arena is a 24 inch but not a 24x1 3/8's that tire would be a 540mm. NW-Will gave you some spot-on information. I have never used the Shox but I have heard they are a bear to get on the rim
    Thanks, I suppose I've learned a lesson that when changing tyre brands its best to ask my wheelchair shop to do it. At least they will be able to try other sizes if they don't fit.

  6. #6
    Senior Member robotnik's Avatar
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    Quote Originally Posted by niallel View Post
    Schwalbe Marathon Plus tyres which are marked 25-559 26" X 1.
    If you don't want to make a mistake, you have to read ONLY the ETRTO size, which is in millimeters. Imperial chart is very confusing.
    25-559 is for a tire with 25mm width, and which fits a 559 mm rim. This last measure is easy to control if you have the rim (outside diameter) but a little tricky to see on the tire, as there's a part of the sidewall which goes inside the rim.
    In your case, the Shox SHOULD fit your rims. They are a bit narrower (20mm instead of 25) but 559 indicates same rim diameter.
    Don't worry about the EXTERNAL diameter of the tire, a narrower tire has also lower sidewalls, so it's external size is smaller (explaining while the Shox fits inside the Schwalbe)
    I hope to be crystal clear ?
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  7. #7
    Quote Originally Posted by niallel View Post

    I wanted solid tyres (had too many punctures when travelling alone) so I bought some Shox G2 which are 20-559.
    Can you tell us the circumstances of your tire punctures with the schwalbe marathons?

    ive been running marathons for the last 10 year and have never had a puncture, despite rolling over glass multiple times, dropping off curbs, and taking the chair camping several times. I’ve had tube failures, but never a puncture.

  8. #8
    Senior Member brian's Avatar
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    Redundant but I'll always repost this for clarity

    Quote Originally Posted by brian View Post
    When sizing wheels and tires, DO NOT use inches. Only use ETRTO sizing. ETRTO is an international standard of sizing.
    Look for a number like "25-540" on the side of your tire. The larger number (540 in this case) is the diameter.

    This is because several different ETRTO sizes of wheel and tire are called 24" depending on its use.
    And 559 ETRTO size is called both 25" for wheelchairs and 26" for bikes.

    ONLY use the ETRTO sizes when measuring and purchasing wheels and tires or you could buy items that don't fit or have trouble finding thins in the correct ETRTO size.
    See this thread for how only measuring in inches can cause problems.
    If you go to a bike shop or online anywhere that's not specifically a wheelchair store and buy a 24" tire, it will NOT fit on your chair.

    24" means ETRTO 540 for wheelchairs and ETRTO 507, 520, and 547 for bikes
    25" means ETRTO 559 for wheelchairs
    26" means ETRTO 590 for wheelchairs and ETRTO 559, 571, 584, and 597 for bikes
    27" means ETRTO 622 for wheelchairs and 700c for bikes

    or, broken down differently:

    ETRTO 507 = 24" for bikes
    ETRTO 520 = 24" for bikes
    ETRTO 540 = 24" for wheelchairs
    ETRTO 547 = 24" for bikes (not common)
    ETRTO 559 = 26" for bikes and 25" for wheelchairs
    ETRTO 571 = 26" for bikes (not common)
    ETRTO 584 = 26" or 650B for bikes
    ETRTO 587 = 26" for bikes (not common)
    ETRTO 590 = 26" for bikes and 26" for wheelchairs
    ETRTO 597 = 26" for bikes (not common)
    ETRTO 622 = 29" and 700c for bikes and 27" for wheelchairs

    It's easy to see why ETRTO is so important to get an exact tire size. Just saying "I need a 26" tire" could be a mistake depending on who you're talking to.


    Quote Originally Posted by NW-Will View Post
    just saying..

    your 26" should be ETRTO 590 for wheelchairs
    and
    27" for wheelchairs is ETRTO 622
    You're right! (corrected)
    Last edited by brian; 02-18-2019 at 10:57 PM.

  9. #9
    Senior Member NW-Will's Avatar
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    just saying..

    your 26" should be ETRTO 590 for wheelchairs
    and
    27" for wheelchairs is ETRTO 622

    Quote Originally Posted by brian View Post
    Redundant but I'll always repost this for clarity



    If you go to a bike shop or online anywhere that's not specifically a wheelchair store and buy a 24" tire, it will NOT fit on your chair.

    24" means ETRTO 540 for wheelchairs and ETRTO 507, 520, and 547 for bikes
    25" means ETRTO 559 for wheelchairs
    26" means ETRTO 622 for wheelchairs and ETRTO 559, 571, 584, 590 and 597 for bikes

    or, broken down differently:

    ETRTO 507 = 24" for bikes
    ETRTO 520 = 24" for bikes
    ETRTO 540 = 24" for wheelchairs
    ETRTO 547 = 24" for bikes (not common)
    ETRTO 559 = 26" for bikes and 25" for wheelchairs
    ETRTO 571 = 26" for bikes (not common)
    ETRTO 584 = 26" or 650B for bikes
    ETRTO 587 = 26" for bikes (not common)
    ETRTO 590 = 26" for bikes
    ETRTO 597 = 26" for bikes (not common)
    ETRTO 622 = 29" and 700c for bikes and 26" for wheelchairs

    It's easy to see why ETRTO is so important to get an exact tire size

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